Estoy desarrollando una aplicación para iOS que permite a los usuarios tomar una secuencia de fotos; luego, las fotos se colocan en una animación y se exportan como MP4 y GIF.

Mientras que el MP4 presenta la calidad de la fuente, los grados de color GIF son visibles.

Aquí la comparación visual:

GIF:

MP4

El código que uso para exportar como GIF:

var dictFile = new NSMutableDictionary();
        var gifDictionaryFile = new NSMutableDictionary();
        gifDictionaryFile.Add(ImageIO.CGImageProperties.GIFLoopCount, NSNumber.FromFloat(0));

        dictFile.Add(ImageIO.CGImageProperties.GIFDictionary, gifDictionaryFile);

        var dictFrame = new NSMutableDictionary();
        var gifDictionaryFrame = new NSMutableDictionary();
        gifDictionaryFrame.Add(ImageIO.CGImageProperties.GIFDelayTime, NSNumber.FromFloat(0f));

        dictFrame.Add(ImageIO.CGImageProperties.GIFDictionary, gifDictionaryFrame);


        InvokeOnMainThread(() =>
    {
        var imageDestination = CGImageDestination.Create(fileURL, MobileCoreServices.UTType.GIF, _images.Length);

        imageDestination.SetProperties(dictFile);

        for (int i = 0; i < this._images.Length; i++)
        {
            imageDestination.AddImage(this._images[i].CGImage, dictFrame);

        }
        imageDestination.Close();
    });

El código que uso para exportar como MP4:

var videoSettings = new NSMutableDictionary();
            videoSettings.Add(AVVideo.CodecKey, AVVideo.CodecH264);
            videoSettings.Add(AVVideo.WidthKey, NSNumber.FromNFloat(images[0].Size.Width));
            videoSettings.Add(AVVideo.HeightKey, NSNumber.FromNFloat(images[0].Size.Height));

            var videoWriter = new AVAssetWriter(fileURL, AVFileType.Mpeg4, out nsError);
            var writerInput = new AVAssetWriterInput(AVMediaType.Video, new AVVideoSettingsCompressed(videoSettings));

            var sourcePixelBufferAttributes = new NSMutableDictionary();

            sourcePixelBufferAttributes.Add(CVPixelBuffer.PixelFormatTypeKey, NSNumber.FromInt32((int)CVPixelFormatType.CV32ARGB));

            var pixelBufferAdaptor = new AVAssetWriterInputPixelBufferAdaptor(writerInput, sourcePixelBufferAttributes);

            videoWriter.AddInput(writerInput);

            if (videoWriter.StartWriting())
            {
                videoWriter.StartSessionAtSourceTime(CMTime.Zero);

                for (int i = 0; i < images.Length; i++)
                {
                    while (true)
                    {
                        if (writerInput.ReadyForMoreMediaData)
                        {
                            var frameTime = new CMTime(1, 10);
                            var lastTime = new CMTime(1 * i, 10);

                            var presentTime = CMTime.Add(lastTime, frameTime);
                            var pixelBufferImage = PixelBufferFromCGImage(images[i].CGImage, pixelBufferAdaptor);

                            Console.WriteLine(pixelBufferAdaptor.AppendPixelBufferWithPresentationTime(pixelBufferImage, presentTime));
                            break;
                        }
                    }
                }

                writerInput.MarkAsFinished();
                await videoWriter.FinishWritingAsync();

Agradecería su ayuda!

Saludos cordiales,

Andre